As with all things, it depends on the exact materiel and construction.

It appears you are describing a monocoque vs spaceframe. The stressed skin has the potential to have much higher stiffness to weight ratio.
If it's just a box, with 12 structural members along the edges, the proper hollow box will be stiffer. This is because a cube would need to be cross braced.

The 'resisting bending' idea is the right concept but wrong direction. For a stiff structure you ideally want no member experiencing any bending, so any 'bending' is eventually taken by a member in tension or compression.